On Wed, Nov 19, 2014 at 7:22 AM, Daniel Stone <dan...@fooishbar.org> wrote:
> Hi, > > On 19 November 2014 14:58, Derek Foreman <der...@osg.samsung.com> wrote: > >> Since we're sort of on the topic, is there anywhere we gain anything >> from y-x banded regions? I'm wondering if it would be worthwhile to >> replace pixman's region code with something that doesn't band. I think >> this would let us drop the pixman dependency when not building the >> pixman renderer... > > > Not really, no. Pixman only does it because the X server requires regions > to be marked as YX-banded to be deigned valid (or 'complete', as an FBO > analogy), and a number of the rendering algorithms in the server depend on > it. > > We don't have any of that, so can happily do without banding. A patch to > Pixman which would optionally drop the strict banding would be nice, but if > there's a small enough region implementation we could use instead, that > could work. > It's more that the algorithms for combining regions only work in the case where you have a vertically-sorted list of horizontal bands. So, you would have to come up with an entirely new algorithm for pixman_region_union, pixman_region_subtract, etc. if want some other format. What's the format you're suggesting? If we flip the axes (horizontally sorted list of vertical bands), then it will work fine for the move up/down case, but break for the left/right case. Derek's approach of post-processing the bands to make a minimal set of overall rectangles seems fine to me. If we only need union, then we could very simply create our own region class that did what we wanted. [0] [0] Or steal http://cgit.freedesktop.org/plymouth/tree/src/libply/ply-region.c > Cheers, > Dan > > _______________________________________________ > wayland-devel mailing list > wayland-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/wayland-devel > > -- Jasper
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